[SR-6935] Can't call Objective-C generic class method from protocol extension.

[krzyzanowskim]

Previous ID	SR-6935
Radar	None
Original Reporter	@krzyzanowskim
Type	Bug

Attachment: Download

Environment

Xcode 9.2, Swift 4.0.3

Additional Detail from JIRA

Votes	0
Component/s	CodeCompletion, Compiler
Labels	Bug
Assignee	None
Priority	Medium

md5: 740486f48fd304f2b204d450e147db01

Issue Description:

I can't explain what is going on, but I can't call the method that is autocompleted, and definitely exists.

protocol _PSPDFKVOController: class {}
extension _PSPDFKVOController {
    func observe2<Value>(_ object: AnyObject, keyPath: KeyPath<Self, Value>, options: NSKeyValueObservingOptions = [], block: @escaping (NSKeyValueObservedChange<Value>) -> Void) -> NSKeyValueObservation? {
        let controller = self as! PSPDFKVOController<Value>
        controller.observe(controller, "", options: options) { (a, b, c) in // Error: Extra argument in call
            // WAT?
        }
}

PSPDFKVOController is an Objective-C generic class

See attached video to see what's going on.